Abstract: To obtain a structure wherein water having entered the gap between the bottom surface of an annular groove in a rotation-side flange and the inside surface in the axial direction of the brake rotor can be easily drained to the outer space. The outer diameter DO of the annular groove 15 is larger than the diameter DDI of the inscribed circle of the opening portion outside in the axial direction of the water drain holes 17a and is smaller than the diameter DDO of the circumscribed circle of the opening portion outside in the axial direction of the water drain holes 17a.

Abstract: A hub unit bearing includes a stationary side raceway ring, a rotating side raceway ring including a rotating side flange for fixing a vehicle wheel, and rolling elements rollably provided therebetween. The rotating side flange includes thin portions and thick portions arranged alternately in a circumferential direction. A hub bolt is serration-fitted to a bolt hole formed in each of the thick portions. An outer peripheral surface of the rotating side flange includes a large-diameter portion which has a larger radial thickness dimension with the bolt hole, a small-diameter portion which has a smaller radial thickness dimension with the bolt hole than the large-diameter portion, and a step portion which connects the large-diameter portion to the small-diameter portion. A serration-fitted portion does not radially overlap with the large-diameter portion.

Abstract: A hub unit bearing includes a stationary side raceway ring, a rotating side raceway ring including a rotating side flange for fixing a vehicle wheel, and rolling elements rollably provided therebetween. The rotating side flange includes thin portions and thick portions arranged alternately in a circumferential direction. A hub bolt is serration-fitted to a bolt hole formed in each of the thick portions. An outer peripheral surface of the rotating side flange includes a large-diameter portion which has a larger radial thickness dimension with the bolt hole, a small-diameter portion which has a smaller radial thickness dimension with the bolt hole than the large-diameter portion, and a step portion which connects the large-diameter portion to the small-diameter portion. A serration-fitted portion does not radially overlap with the large-diameter portion.

Abstract: To obtain a structure wherein water having entered the gap between the bottom surface of an annular groove in a rotation-side flange and the inside surface in the axial direction of the brake rotor can be easily drained to the outer space. The outer diameter DO of the annular groove 15 is larger than the diameter DDI of the inscribed circle of the opening portion outside in the axial direction of the water drain holes 17a and is smaller than the diameter DDO of the circumscribed circle of the opening portion outside in the axial direction of the water drain holes 17a.

Abstract: The portion axially opposed to an encoder 13a in a bottom part 23a constructing the cap 19a for closing an opening of an axially inboard end of an outer ring 2 is formed with a through hole 25a pierced in an axial direction. And, the bottomed cylindrical sensor insertion case 26a made of a non-magnetic material is axially inserted into an inside of the through hole 25a with a bottom plate part 35a facing to the lead, and is internally fitted to the inside of the through hole 25a. Also, a rubber O ring 56 is pinched in annular space 55 formed between an outer peripheral surface of a cylindrical part 39a constructing the sensor insertion case 26a and an inner peripheral surface of a middle-diameter hole part 53 constructing the through hole 25a in a state having a radial interference.

Abstract: The portion axially opposed to an encoder 13a in a bottom part 23a constructing the cap 19a for closing an opening of an axially inboard end of an outer ring 2 is formed with a through hole 25a pierced in an axial direction. And, the bottomed cylindrical sensor insertion case 26a made of a non-magnetic material is axially inserted into an inside of the through hole 25a with a bottom plate part 35a facing to the lead, and is internally fitted to the inside of the through hole 25a. Also, a rubber O ring 56 is pinched in annular space 55 formed between an outer peripheral surface of a cylindrical part 39a constructing the sensor insertion case 26a and an inner peripheral surface of a middle-diameter hole part 53 constructing the through hole 25a in a state having a radial interference.